1. Field of the Invention
The present invention relates to systems for conveying solid particles through gas flows, and more particularly to coal pulverizer (mill) discharge piping systems wherein coal particles are conveyed through air flows.
2. Description of Related Art
In coal combustion systems, coal and primary air (PA) flow distribution between burner lines is important for optimizing combustion and burner performance. Low NOX burner design usually requires that coal mass flow imbalance between coal pipes should be within +/−15% deviation from the mean value, or lower, to ensure burner performance. Imbalanced coal flow between coal pipes also negatively impacts combustion efficiency, as indicated by unburned carbon (UBC), heat rate, etc., as well as gaseous emissions such as NOX, CO, etc. Orifices (fixed or variable) installed in the coal pipes for PA (primary air) flow adjustment are unable to correct the coal flow imbalance without having adverse effects on the PA flow distribution, when this imbalance is a result of uneven coal flow discharged from an upstream classifier.
To resolve the coal flow distribution shortcomings in the art, there exists a need in the art for a coal flow distribution system that provides a tool to correct particle flow distribution between coal pipes. There also remains a need in the art for such a system that has little or no negative impact on PA flow distribution between coal pipes. The present invention provides a solution for these problems.